I. Field of the Invention
This invention relates generally to power tool apparatus and more specifically to a universal, multi-purpose power tool specifically designed so that with only modest set-up times, it can be made to function in a wide range of capacities, normally carried out by plural separate single-purpose power tools.
II. Discussion of the Prior Art:
In the Goldschmidt U.S. Pat. No. 2,623,269 there is described a convertible power tool which may be set up to function as any one of a plurality of material working tools, such as a drill press, table saw, lathe or sander. The present invention is deemed to be a significant improvement over that design in at least the following respects:
(1) Ease of set-up; PA1 (2) Degree of precision attainable; PA1 (3) Flexibility of use; PA1 (4) Variability in rotary tool speed; PA1 (5) Motor driven power carriage control; PA1 (6) Vernier control on power carriage motion; PA1 (7) Positive locking of power head and power carriage; PA1 (8)Ability to accommodate workpieces of varying sizes and lengths.
The device of the Goldschmidt Patent, for example, does not provide motor powered translation of either its headstock or the workpiece supporting carriage and, accordingly, that device cannot function as a vertical or horizontal milling machine or as a boring machine. Further, the overall construction of the device reflected in the Goldschmidt Patent seriously limits the precision with which workpieces can be machined or shaped. Specifically, because the locking arrangements by which the headstock and carriage are secured to the ways do not afford a sufficient degree of rigidity to preclude misalignment and movement due to vibration and the like.
Also inhibiting the flexibility and ease of use of the prior art Goldschmidt tool is the fact that in converting the machine between a horizontal and a vertical orientation, no means are provided for counterbalancing the parallel ways and, accordingly, the operator must lift or support the entire weight in moving the ways from the horizontal to the vertical and vica versa.
The design of the present invention obviates most of the foregoing drawbacks of the prior art. Specifically, positive, two-point locking is provided between the power head and its cooperating ways as well as between the power carriage and the ways. Further, in the device of the present invention a counterbalance in the form of a heavy coil spring is provided which facilitates the repositioning of the ways between the horizontal and the vertical. Further, by providing a power drive on the tool supporting carriage and by providing a precise vernier control over the carriage drive motor rotational speed, it is possible to advance a workpiece towards a stationary cutting tool at a wide range of rates ranging from fractions of inches per second on up. As such, through proper selection of the cutting tool, the universal power tool of the present invention can be made to function as either a milling or a boring machine, thereby expanding the adaptability of the tool over the prior art as represented by the Goldschmidt Patent.